Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Pentax / Samsung dSLR, K Mount Mirrorless

Reply
 
Thread Tools Search this Thread
Old Dec 8, 2006, 6:58 PM   #1
Senior Member
 
Join Date: Jun 2006
Posts: 400
Default

I am giving my *ist DS a walk along the river bank just about every day during my lunch-time break from the salt works. My efforts so far has been towards developing a few basic skills in capturing the few bird types there are around here. Mainly water fowl, some high tree canopy birds and "town" birds like sparrows and pidgeons.

My lens is usually a Sigma 450mm f5.6 which having been rescued from the scrap heap and its Minolta mount removed is now fully manual in both focus and aperture. I usually use it wide open.

Recent discussions concerning teleconverters and mention that the Pentax autofocussing 1.7x teleconverter gives auto focus to manual lens gave me the idea that maybe I could have autofocus on my old long lenses.

The local Pentax outlet tells me the Pentax 1.7X TC would cost me about US$270 which is just a little more than I spend without thinking about it a little.

Prospective candidates for mating to the Pentax TC include:

450mm 5.6 Sigma hacked K mount, no aperture levers.

450mm 6.5 Tele Lentar M42 mount

300mm f4 Takumar M42 mount

500mm f8 Sigma mirror lens.

My estimation is that the Takumar would give the best combination of reach and speed and this is the one I should test the Pentax TC with.

Any comments?



Thanks








John Hill is offline   Reply With Quote
Sponsored Links
Old Dec 8, 2006, 8:00 PM   #2
Guest
 
Posts: n/a
Default

i've tried my 300 f4with a 2x and all i can say is forget handholding it. mine is a 600mm f8 and your's would be 510mm f8. i just don't think it's really plausible to shoot at these mags and get what you want. i even doubt that the TC would even work with the lens wide open in AF mode..

john, please prove me wrong,
roy
  Reply With Quote
Old Dec 8, 2006, 9:41 PM   #3
Senior Member
 
snostorm's Avatar
 
Join Date: Jan 2004
Location: Chicago Suburb, IL, USA
Posts: 2,770
Default

Hi John,

The literature with the PF 1.7AFA recommends lenses that are F2.8 or faster. I'm not a believer in following recommendations unless there is grave danger implied, and since the only thing that could go wrong was that it wouldn't AF, I started using it with an A*300 f4, and it worked fine. I later got an FA*300 f4.5 and it works great on this lens also in reasonable light. I have heard reports that it doesn't AF well with some lenses in the f4 max aperture range, but I can't personally attest to this claim, though it makes some sense in that the two Pentax * 300s are extremely sharp, even wide open, so this would help the AF even if they are slower than recommended.

IMO, the Takumar 300/4 might have a chance, but I know that it isn't nearly as sharp as the * class 300s. The rest of the lenses probably won't. That's not to say that the TC won't work, it just won't AF reliably, if at all.

BTW, this is my favorite TC -- use it all the time for birding. It's a very high quality TC, and shows very little image degradation when used with a very good lens. IMO, if you can get one, it's worth the investment, but US$270 is pretty steep. Of course, YMMV.

Scott
snostorm is offline   Reply With Quote
Old Dec 8, 2006, 10:03 PM   #4
Senior Member
 
Join Date: Jun 2006
Posts: 400
Default

I have just done a few tests with a yard rule taped up 12 metres from where I set up the tripod.

Needless to say the Sigma 600mm f8 mirror with the Vivitar 2x teleconverter gave a very poor result.

The mirror lens alone gave a fair result.

The Takumar 300 f4 gave a good result

The Takumar 300 f4 on the teleconverter gave a much better result than the 600 mirror alone

All shots ISO 800.

The two mirror shot at the top and the two Takumar shots below. All 100% crop.








John Hill is offline   Reply With Quote
Old Dec 8, 2006, 10:15 PM   #5
Senior Member
 
snostorm's Avatar
 
Join Date: Jan 2004
Location: Chicago Suburb, IL, USA
Posts: 2,770
Default

Hi John,

Did you use the 2 sec timer with MLU? The 600mm w/2x looks like camera shake to me, but of course I could be wrong.

Scott
snostorm is offline   Reply With Quote
Old Dec 8, 2006, 10:27 PM   #6
Senior Member
 
Join Date: Jun 2006
Posts: 400
Default

Hi Scott, I used the 2 sec timer on them all. If you think that is camera shake I will go and set up some bean bags or something. We have a timber framed house and a strong wind today which could, I guess, cause visible shakes.

Thanks.
John Hill is offline   Reply With Quote
Old Dec 8, 2006, 10:33 PM   #7
Senior Member
 
Join Date: Jun 2006
Posts: 400
Default

Scott, is "PF 1.7AFA" the official Pentax designator for what I am looking for, which is a TC that will provide auto focus to manual lenses?

If I have a reliable designator I can search the world for one otherwise I would be loath to spend any money on something that might turn out to be not what I seek plus the hassle of a, maybe impossible, international return.

Testing with my Takumar 300 f4 and the Vivitar 2x TC gets the autofocus red square to show readily enough, do you think this is a fair indicator of potential success with the auto focus TC?



John








John Hill is offline   Reply With Quote
Old Dec 8, 2006, 11:01 PM   #8
Senior Member
 
snostorm's Avatar
 
Join Date: Jan 2004
Location: Chicago Suburb, IL, USA
Posts: 2,770
Default

Hi John,

The official designation is

SMC Pentax F- 1.7x AF Adapter

From the side of the lens.

Scott


I forgot to add that if the AF indicator lights up consistently and focus is easy to find with it, then there's a reasonable possiblity that it would work in good light -- but I have to warn you that there's still a chance it might not work. -- and I just remembered something else -- with an M42 lens w/ adapter, you might have to short out the pins (electrical contacts) on the lens mount side of the adapter with tin foil to get it to AF correctly.
snostorm is offline   Reply With Quote
Old Dec 8, 2006, 11:23 PM   #9
Senior Member
 
Join Date: Jun 2006
Posts: 400
Default

Thanks Scott, with that designator I can confidently search for sources.

I think what I really need to do now is to look for a really fast lens of less than 300mm, when, if I find one I can reconsider the TC.

BTW, I set the camera up again on bean bags etc and got a much better shot with the mirror and TC but really that is beside what I am trying to do as there is no way I could ever handle a virtual 1200mm f16 combination in the field. I would need to take a barrow load of concrete along and pour foundations for every shot!:-)
John Hill is offline   Reply With Quote
Old Dec 9, 2006, 6:23 AM   #10
Guest
 
Posts: n/a
Default

john,
any lens over 400mm f5.6 is not going to be hand holdable. it's too much weight and too much magnification. i've tried with a 400 at 5.6 and it's a really tough situation. you may get a shot or 2 but the majority are going to be junk. add the 2Xs image degradation and i don't think you'll be happy. disclaimer+ if you start with a $2000 lens with the 2X you may be happy with the result, but......hand holdable????

roy
edit: none of the lenses you have listed are going to give acceptable results, IMHO, by themselves wide open , much less with a TC.
  Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 5:37 PM.